Aeolus Airship: Human-Powered Blimp: TreeHugger
Setting the bar pretty high for airship design is this one from Christopher Ottersbach: Called the Aeolus Airship (named after Aeolus, the Greek wind god) it is designed to be aerodynamic than conventional airship designs, and stay aloft for up to two weeks on a supply of helium and, furthermore, is pedal-powered by the crew of 2-4 people.

Beautiful. Like something out of a Japanese Anime. More on Inhabitat.